1. Field of the Invention
The present invention is directed to the forming of a material, and more particularly, to a process for drawing or stamping predetermined portions of a material which has been subjected to a localized heat treatment ("retrogression heat treatment") method.
2. Background Art
The forming of a metallic material/metal into a desired shape, by drawing or stamping has been known in the art. With some metallic materials, such an operation often times disrupts the structural integrity of the metallic material. Indeed, many metals and alloys have unstable tempers, which do not lend themselves to stamping/drawing. Thus, it has been standard practice to use only metals of certain stable tempers for such operations.
For instance, in the sheet metal industry, stable, age hardened materials (such as alloys with stabilized -T4 tempers) or fully annealed materials are used in order to achieve maximum formability in stamping or drawing operations. While such materials have been useful, in many applications it is desirous to use an even harder alloy, such as an aluminum alloy having -T6 temper properties.
In particular, unsatisfactory results have been observed with the drawing/stamping of many types of aluminum alloys (not to mention other metallic materials). For example, a -T4 temper aluminum alloy material is desirable from a ductility and strength standpoint for use in stamping operations. One such advantage is that it does not need to be solution annealed in order to be able to approach stronger -T6 temper properties in the finished components) (the -T4 temper materials need only be aged at moderate temperatures for short periods of time to achieve near or full -T6 temper properties). However, there are drawbacks to using an unstable -T4 temper material in stamping operations inasmuch as the -T4 temper is long-term unstable. Due to its instability, if a -T4 temper material is used to make a component (through a drawing or stamping process) the drawn/stamped region can develop cracks during the drawing operation, and would, if readily formable, be desirous for use in many applications. As such, the component is defective and unusable.
On the other hand, a -T5 or a -T6 temper aluminum alloy is stable. However, it is difficult to draw or stamp such a material. Indeed, the material is generally too brittle to permit forming through such processes. As such, if any drawing or stamping is attempted with such a material, the material quickly deteriorates and cracks develop. Thus, this material is likewise unsuitable for any such processes.
It is thus an object of the present invention to provide a method for stamping or drawing hard metallic materials which are conventionally deemed unacceptable for such stamping or drawing.
It is also an object of the present invention to draw or stamp such metallic materials at predetermined regions, wherein the predetermined regions have stretched (or drawn) areas having depths greater than conventionally obtainable--without the formation of any visually observable cracking in the stretched/drawn areas.
These and other objects of the present invention will become apparent in light of the present Specification, Claims and Drawings.